Schedule of Details Supporting Computation of Earnings Per Share (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 344	$ 420	$ 712	$ 893
Weighted average outstanding shares of common stock used to compute basic earnings per common share	155,423	157,975	155,257	158,446
Shares used to compute diluted earnings per common share	157,046	159,521	156,846	159,962
Basic earnings per common share	$ 2.22	$ 2.66	$ 4.59	$ 5.64
Diluted earnings per common share	$ 2.19	$ 2.63	$ 4.54	$ 5.58
Number of antidilutive stock options and restricted stock excluded from computation	245	847	609	1,265
Employee Stock Options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock	227	349	248	367
Restricted Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock	1,396	1,197	1,341	1,149